Posted
by
Soulskillon Wednesday October 24, 2012 @01:19AM
from the but-does-it-run-linux dept.

An anonymous reader writes "Anybody think 3-D printing technology will have enough moxie to pull off a construction of Babbage's analytical engine by 2021, the 150th anniversary of Babbage's passing? The Guardian reports, 'Plan 28 – named after one set of Babbage's plans – has assembled the leading technical experts on his designs and just started fundraising. The first stage of the project involves studying the thousands of pages of handwritten notes that Babbage left behind, to determine what exactly needs to be built. Once the study is complete, we'll be building a 3D physical computer simulation of the analytical engine to verify that his design is workable. Reaching that stage is likely to cost about £250,000. Only once the feasibility of building the machine has been established will the much larger fundraising effort needed for the actual construction to begin. But what we hope to do is create a working monument to the man who conceived the computer, and to inspire today's scientists and engineers to dream a century into their future.'"

plenty of 3D model enthusiasts are making very complex files as a hobby on consumer grade computers, but these "pros" can't seem to be able to replicate a 19th century design without needing hundreds of thousands of dollars?

To be more specific: with so many toothed wheels it's not just a problem in recreating logical process flow. What are the allowable tolerances for the thing not to jam? What are the necessary tolerances for the thing to move at all, lubricated or not? Is there even a window of tolerance where the thing can complete its moves without jamming?

Interestingly tolerances are exactly the main problem : in Babbage's time every gear was handcut, so highly variable. Worse, since there were literally no industrial standards, even a simple nut and bolt, unless cut on the exactly the same lathe, would not work together! The parts were all individual, the idea of interchangeable identical parts is a remarkably powerful one, but not one Babbage could rely on at the time.
Its amazing what has changed on that front...

The British government funded Babbage ultimately to the tune of roughly 17000 Pounds, which would today be equivalent to somewhere between 1.3 and 1.6 million Pounds.

Sooo... yeah. Babbage was a tinkerer. And while that's all good, turns out that at some point you have to sit down, declare feature freeze and just build something. Otherwise your investors will get tired of hearing about how many improvements you've come up with. And so will your machinist. Something, something, perfect, enemy, good...

Last great finished work: B minor mass. Big CATHOLIC mass in old rite. Inconceivable to play in his own protestant church. Inconceivable to play in catholic churches any more. At that point of time, inconceivable to play sacred music in secular circumstances. He was dead for longer than he had lived (and he lived to a reasonably long age) when this thing saw its first full performance.

And what a work.

As contrasted to Babbage, he most certainly was aware that the time for his magnum opus was quite not ready.

That project is starting to sound like a boondoggle. Lots of PR and fundraising, no hardware. They have a contribution system, a mailing list, a Twitter feed, and press coverage. They've been blithering about this for two years now. But they haven't built so much as one single demo part.

We know what the Analytical Engine was supposed to do computationally. There's a simulator. [fourmilab.ch] It's a rather straightforward machine. It's roughly comparable to a programmable calculator of the 1970s. There are 1000 memory locations, each of which stores a 50-digit decimal number. These are separate from the program and data, which are on chains of punched cards. It can add, subtract, multiply, divide, shift, and compare, which is all you need.

There's no good reason for the 50-digit precision, and 1000 memory locations is too much for the compute power available (about 1 IPS). Like programmable calculators, 10 digits and 100 memory locations would have been enough for most problems. Babbage's own trial model of the "mill" (the ALU) has only 25 digits. Building a memory of 50,000 wheels about 3 inches in diameter means building something the size of a locomotive, most of which will just sit there. Trimming it down to 25 digits and 100 locations would make for a large desk-sized machine.

A question I once asked of the project was "how many part numbers"? That is, how many different parts are required? They didn't know. I suspect not that many. The existing model of the mill doesn't have a high part number count. The "store" (the memory unit) is inherently repetitive. Most of the parts can be die-cast and finish-machined, which is the most economical way to produce good metal parts in medium quantity. Many of the lever-type parts are cut from flat sheets of brass. Those you make with a CNC mill or a water jet cutter. 3D printing isn't really appropriate as a way to make brass parts, and making a plastic copy of the Analytical Engine would be rather tacky.

I didn't realize my old account had expired. Damn, I'd had that since 2003. Anyway, I logged in to mod this one up and that started this entire debacle. Must have been quite some time since I was inspired to log in instead of just reading anonymously.

You are quite correct that we have not built a single demo part. In the two years since I started talking about this project the following has happened:

1. Persuaded the Science Museum to digitize all of Babbage's plans and notebooks (this in itself was a non-trivial task involving a great deal of effort at all levels and they should be thanked for taking on the task).2. Got the leading Babbage experts to join and work with me (Doron Swade who built the Difference Engine No. 2 and Tim Robinson)3. Started a UK-based charity (again these things take time as there are legal requirements and the recruitment of a board of trustees)4. Started research on the Babbage archive itself5. Begun fund-raising.

No. 4 is non-trivial because there are literally thousands of pages of notes and > 230 large scale plans to decipher. Plus there's a hardware description language to work with. And the archive is not well documented. There are a number of different cross references that conflict with each other. I realize that all this stuff is boring and people would like to see an immediate result, but that's not going to happen. It's years of work to properly study this stuff and build a historically accurate machine.

Note that we have not proposed building the 1,000 memory location machine. That's far too much to demonstrate that it would work and would add to the cost and size. As for the number of parts, until we've deciphered all the plans and come up with a definitive plan that it's hard to answer but we believe there will be roughly 40,000 to 50,000 components to be made.

There's no good reason for the 50-digit precision, and 1000 memory locations is too much for the compute power available (about 1 IPS). Like programmable calculators, 10 digits and 100 memory locations would have been enough for most problems.

No, you are mistaken. Such programmable calculators have 10 digits of *precision* plus an exponent. In other words, they store floating point numbers. The analytical engine was fixed-point, so far more digits were required for many calculations.

Floating point arithmetic wasn't invented theoretically until 1914. A working physical model didn't appear until 1938 or so.

3D printing isn't really appropriate as a way to make brass parts,

3D selective powder sintering can print 3D brass parts. Though you are correct, for sheets CNC jet cutting is better and for the quantity of gears required casting would be better.

Such programmable calculators have 10 digits of *precision* plus an exponent. In other words, they store floating point numbers. The analytical engine was fixed-point, so far more digits were required for many calculations.

Mechanical desk calculators usually had about 10 or 12 digits of precision, with a double-length product register on the carriage. They were fixed-point devices. Babbage was familiar with early versions of such devices [wikipedia.org], his writings discuss fixed point scaling, and his machine has a decimal shift capability.

3D printing isn't really appropriate as a way to make brass parts, and making a plastic copy of the Analytical Engine would be rather tacky

Not to mention that an analytical engine made in 3d-printed plastic (ABS, nylon, etc., depending on the specific technology) probably wouldn't work. Back in the day I designed the mechanics of a grandfather clock in CAD. On a lark, I got to go-ahead to print off a number of parts on the school's stratasys (an FDM machine that extrudes hot ABS). When I started putting things together, I realized that the project would not work very well. The surface finish and dimensional tolerance made for high friction and occasional binding. Plus, the cost of most of these parts was really high - several times the cost of mass-produced gears from, say, stockdriveproducts.com [sdp-si.com]. So, instead, I scrapped the fully custom design I had been working on, and remade it using slightly different-but-vastly-higher-quality-at-lower-price parts available off the shelf.

You'd be surprised where 3d printing has gone in the last few years. Maybe it's not to the point that your clock project would be feasible today, but well tuned homebrew 3d printers already surpass the accuracy and resolution of many commercial printers. Check this out as an example. [reprap.org] The technology is improving and becoming more accessible. If you told someone looking at the first Altair that one day they'd use a similar machine to share intimate details of their lives with strangers on the other side o

I found the Java applet interesting. I was wondering if anyone ever did a CAD mockup of a working difference engine? I did some gear boxes in TrueSpace back in the day which took some effort. I believe you can do a lot a scripting in Studio Max and it might have the power of creating a simulacrum of a Babbage computer. Once the basic mechanisms have been crafted they could be cloned and reused ad infinitum.

Can an expert on modern English comment on the summary's use of the word "moxie" as presumably meaning "capable". I have always thought "moxie" to be something only a person could have and mean "strength of character" or similar. Is there a difference in American versus British English?

Here's another questionable choice of words in the summary: "Once the study is complete, we'll be building a 3D physical computer simulation of the analytical engine to verify that his design is workable." 3D "physical" computer "simulation"?

Can an expert on modern English comment on the summary's use of the word "moxie" as presumably meaning "capable". I have always thought "moxie" to be something only a person could have and mean "strength of character" or similar. Is there a difference in American versus British English?

Moxie is purely an American word. I've never heard or read it in the UK, and had to google it to find out what it meant. The drink from which the word derives is not one that I'vve ever seen or heard of here in the UK either.

Although the subject matter of the story is British, the submitter is presumably American.

We'd need a revolution in 3D printing to make printing an Analytical Engine feasible.A machine like the Analytical Engine puts significant stress on its gears and shafts. The current crop of metal printers use sintering, which does not yield a very strong part. You'd need a printer that can create parts that rival the strength of cast parts.

... for the accomplishments of Mr. Babbage, but was he really influential?

While Babbage is rightfully admired for his invention, it really had no legacy. No subsequent computer pioneer was either inspired by him, or further pursued his inventions.Can anyone provide a quote or other evidence that early computer pioneers drew upon Babbage's invention for their own work?

Or Howard Aiken, or Flowers, or von Neumann... many computing pioneers acknowledged Babbage specifically. Aiken actually studied a partial Babbage machine built by Babbage's son. Von Neumann even used notation developed by Babba

Alan Turing, for one. I'm pretty sure this is mentioned in the book The Mechanical Mind in History in the essay "Alan Turing’s Mind Machines" by Donald Michie (unless I'm mistaken; it could have been in the biographical film Codebreaker, too. I recently read/watched both). Turing knew of Babbage, but may not have been aware of the particular details of either the Difference Engine or the Analytical Machine. Though, I really wish I had more sources to back this up.

"The first stage of the project involves studying the thousands of pages of handwritten notes that Babbage left behind, to determine what exactly needs to be built."

I know "starting from the beginning" has its merits, but in this case, that's kind of a weird place to start. Instead, why don't you ask for the notes from the Universities who have already done that, and have already built working portions of his machines?